1. Field of the Invention
The field of the invention is arc welding apparatus, and more particularly, circuits for controlling the arc voltages applied by arc welding apparatus.
2. Brief Description of the Prior Art
Arc welding apparatus are well known in the prior art. The quality of the weld is dependent upon maintenance of a proper arc length and voltage. It is desirable that a welding apparatus compensate for changes in welding parameters, introduced by workpiece variations and the like. For example, the workpiece may vary in thickness or resistance, and unless the arc voltage is compensated for such variances, the weld will not be uniform in it characteristics.
In my co-pending application entitled "Welding Apparatus," Ser. No. 372,193 filed Apr. 26, 1983, an apparatus is described for mounting the welding electrode on a fixture which is servo operated to move the electrode in relation to the workpiece. While servo positionable electrodes per se are not new, the servo circuits employed in the past have suffered the disadvantages of oversensitivity to variations in arc voltage, such that the electrode will oscillate or "hunt" for the electrode position at which the nominal arc voltage is obtained. This excessive "hunting" is of course deleterious to the weld.
Accordingly, a need exists for an arc voltage control circuit which maintains the arc voltage within a proper range about the nominal voltage, without excessive servo "hunting."